Fibrous base material for a friction lining material comprising less fibrillated aramid fibers and synthetic graphite

ABSTRACT

The present invention relates to a fibrous base material comprising less fibrillated aramid fibers, synthetic graphite and at least one filler material, and a non-asbestos friction material produced therefrom. In certain embodiments, the fibrous base material is impregnated with a phenolic or phenolic-base resin material, including, for example, a mixture of a phenolic resin and a silicone resin.

TECHNICAL FIELD

This application is a continuation of application Ser. No. 08/535,788filed on Sep. 28, 1995, now abandoned which is a continuation-in-part ofSer. No. 08/253,727 filed Jun. 3, 1994, still pending, which is acontinuation-in-part of Ser. No. 08/101,951 filed Aug. 4, 1993, nowabandoned all of which are expressly incorporated herein by reference.

The present invention relates to a fibrous base material comprising lessfibrillated aramid fibers, manufactured or synthetic graphite and afiller material, such as diatomaceous earth. The invention furtherrelates to a composite friction material comprising the above describedfibrous base material impregnated with a phenolic resin or a modifiedphenolic resin blend. In certain embodiments, at least one siliconeresin is blended with at least one phenolic resin for use inimpregnating a fibrous base material.

The friction material of the present invention has improved strength,porosity and wear resistance. The friction material of the presentinvention also has higher friction stability and thermal capability thanconventional friction materials. The friction material is especiallyuseful in high energy applications.

BACKGROUND ART

New and advanced transmission systems and braking systems are beingdeveloped by the automotive industry. These new systems often involvehigh energy requirements. Therefore, the friction materials technologymust be also developed to meet the increasing energy requirements ofthese advanced systems.

In particular, a new high energy type friction material is needed. Thenew high energy friction material must be able to withstand high speedswherein surface speeds are up to about 65 m/seconds. Also, the frictionmaterial must be able to withstand high facing lining pressures up toabout 1500 psi. It is also important that the friction material beuseful under limited lubrication conditions.

The friction material must be durable and have high heat resistance inorder to be useful in the advanced transmission and braking systems. Notonly must the friction material remain stable at high temperatures, itmust also be able to rapidly dissipate the high heat that is beinggenerated during operating conditions.

The high speeds generated during engagement and disengagement of the newtransmission and braking systems mean that a friction material must beable to maintain a relatively constant friction throughout theengagement. It is important that the frictional engagement be relativelyconstant over a wide range of speeds and temperatures in order tominimize "shuddering" of materials during braking or the transmissionsystem during power shift from one gear to another.

Previously, asbestos fibers were included in the friction material fortemperature stability. For example, the Arledter et al. U.S. Pat. No.3,270,846 patent describes phenolic and phenolic-modified resins usedwith asbestos. Now, however, due to health and environmental problems,asbestos is no longer being used. More recent friction materials haveattempted to overcome the absence of the asbestos in the frictionmaterial by modifying impregnating paper or fiber materials withphenolic or phenolic-modified resins. These friction materials, however,do not rapidly dissipate the high heat generated, and do not have thenecessary heat resistance and satisfactory high coefficient of frictionperformance now needed for use in the high speed systems currently beingdeveloped.

While phenolic resins have found use in friction materials for wetclutch applications, the phenolic resins have various limitations. Thephenolic resin friction materials do not have the high heat resistancenecessary for use with the new high energy transmission systems. Inparticular, the phenolic resins carbonize at a temperature of about 450°to 500° C. which is too low to be useful in high energy applications. Inaddition, phenolic resins are rigid materials and when the phenolicresins are used in a friction material, uneven lining wear and separatorplate "hot spots" result.

Attempts to overcome the limitations and drawbacks of phenolic resinfriction materials include the replacement of phenolic resins with otherthermosetting resins. One attempt to produce friction materials involvesthe modification of a phenolic resin with various synthetic resins. Oneexample, described in Takarada et al. U.S. Pat. No. 4,657,951, is aphenolic resin modified with an organopolysiloxane which is compressionmolded to form a friction material. The phenolic resin andorganopolysiloxane are reacted together to effect a condensationreaction which is then distilled, solidified by cooling, and pulverizedto obtain a powdered phenolic-modified resin. The powderedphenolic-modified resin was used in forming a compression moldedfriction material.

As far as is known, there is no disclosure of a friction material foruse in transmission systems which includes a silicone material blendedwith a phenolic material and used to impregnate a friction paper.

While the Hartmann et al. U.S. Pat. No. 3,911,045 reference discusses asilicone material blended with phenolic resins for use as a compressionmolding composition, there is no disclosure or suggestion that asilicone material could successfully be blended with a resin materialand used to impregnate a friction lining material. On the contrary,previous attempts to use silicone resins in friction materials have beenunacceptable. A friction lining that is impregnated or saturated with asilicone resin has, in the past, demonstrated poor shear strength anddelamination resistance. Further, friction materials saturated with asilicone resin are usually too elastic and therefore tests withundesirable friction and wear characteristics resulting. It is notsurprising that molded friction lining compositions formed entirely of aphenol-formaldehyde resin-polysiloxane resin have not been used eventhough they are known, since such molded compositions do not have thenecessary constant coefficient of friction characteristics and suchfriction materials fail under high energy and high heat conditions.

In order for friction materials to be useful in "wet" applications, thefriction material must have a wide variety of acceptablecharacteristics. The friction material must be resilient or elastic yetresistant to compression set, abrasion and stress; have high heatresistance and be able to dissipate heat quickly; and, have longlasting, stable and consistent frictional performance. If any of thesecharacteristics are not met, optimum performance of the frictionmaterial is not met.

Thus, it is also important that the impregnating resin be used with asuitable friction lining or fibrous base material to form a high energyapplication friction material, The friction material must have goodshear strength both when saturated with the wet resin duringimpregnation and when saturated with brake fluid or transmission oilduring use.

It is also important, under certain applications, that the frictionmaterial have high porosity such that there is a high fluid permeationcapacity during use. Thus, it is important that the friction materialnot only be porous, it must also be compressible. The fluids permeatedinto the friction material must be capable of being squeezed or releasedfrom the friction material quickly under the pressures applied duringoperation of the brake or transmission, yet the lining material must notcollapse. It is also important that the friction material have highthermal conductivity to also help rapidly dissipate the heat generatedduring operation of the brake or transmission.

Other recent friction materials have attempted to overcome the absenceof asbestos fibers by including cellulose or aramid-type pulp or fibers.These aramid-type fibers, however, have relatively fibrillated surfaceswhich allow the fibers to become closely entangled in a friction paper.The entangled fibers cause the resulting friction paper to be dense andhave less than the desired porosity needed for the new high energytransmission systems.

As far as is known, there is no disclosure of a friction material foruse in transmission systems which includes an aramid-type fiber which isless fibrillated than currently available aramid fibers.

Accordingly, it is an object of the present invention to provide animproved friction material with reliable and improved propertiescompared to those of the prior art.

A further object of this invention is to provide friction materials withhigh thermal conductivity, porosity and strength.

As a result of extensive research in view of the need for a betterfriction material, a friction material with improved characteristics hasbeen developed by the invention. The present wet friction material isuseful in "wet" applications where the friction material is "wetted" orimpregnated with a liquid such as brake fluid or automatic transmissionfluid during use. During use of the "wet" friction material, the fluidis ultimately squeezed from or is impregnating the friction material.Wet friction materials differ greatly, both in their compositions andphysical characteristics from "dry" friction materials.

DISCLOSURE OF THE INVENTION

In order to achieve the requirements discussed above, many materialswere evaluated for friction and heat resistant characteristics underconditions similar to those encountered during operation. Bothcommercially available brake linings and transmission materials wereinvestigated and proved not to be suitable for use in high energyapplications.

The present invention is especially useful in brakes and in clutchapplications. The present invention provides a fibrous base materialcomprising less fibrillated aramid fibers, synthetic graphite, at leastone filler material and optionally other ingredients. The fibrous basematerial can be impregnated using different resin systems. In certainembodiments, it is useful to impregnate the fibrous based material witha phenolic resin or a modified phenolic-based resin. It has now beendiscovered that, in certain embodiments, when a silicone resin isblended or mixed with a phenolic resin in compatible solvents and thatsilicone-phenolic resin blend is used to impregnate a fibrous basematerial of the present invention, a high energy friction material isformed. Such high energy friction material has high friction stabilityand high heat resistance.

The friction material of the present invention prevents uneven liningwear and therefore the formation of separator plate "hot spots" fromdeveloping during the useful life of the friction material. When thereis little uneven wear on the friction material, there is more likelihoodto maintain "steady state" of the clutch or brake components andtherefore, more consistent performance of the clutch and brake. Further,the friction material of the present invention shows good shear strengthsuch that the friction material resists delamination during use.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a scanning electron microphotograph of a fibrous basematerial impregnated with a silicone-phenolic blend (Example C).

FIG. 1B is a scanning electron microphotograph of a conventional fibrousmaterial impregnated with a phenolic resin (Conventional-1).

FIG. 2 is a thermal gravimetric analysis (TGA) graph showing therelationship between the percent of weight change and increasestemperatures for a fibrous base material impregnated with a phenolicresin (Example A) or a fibrous base material impregnated with asilicone-phenolic resin blend (Example B).

FIG. 3 is a TGA graph showing the percent of weight loss as temperaturesincrease, the change in the derivative weight (%/°C.), and the amountand percent of residue for Example A shown in FIG. 2.

FIG. 4 is a TGA graph showing the percent of weight loss as temperaturesincrease, the change in the derivative weight, and the amount andpercent of for Example B shown in FIG. 2.

FIG. 5 is a graph showing the stop time in seconds as the number ofcycles increases for a conventional material impregnated with abutadiene phenolic resin (Conventional-1 ) as compared to a fibrous basematerial impregnated with a silicone-phenolic resin blend (Example C)and a fibrous base material impregnated with different epoxy-phenolicresins (Example D 0.016 inch thin lining and Example F 0.020 inch thicklining).

FIG. 6 is a graph showing the ratio of static to dynamic coefficient offriction performance as the number of cycles increases for theConventional-1 material as compared to the Examples C, D and Fmaterials.

FIG. 7 is a graph showing the dynamic coefficient of frictionperformance as the number of cycles increases for the Conventional-1material as compared to the Examples C, D and F materials.

FIG. 8 is a graph showing the dynamic mid point coefficient frictionperformance as the number of cycles increases for the Conventional-1material as compared to Examples B, D and a fibrous base materialimpregnated with a different epoxy phenolic resin (Example E).

FIG. 9 is a graph showing the stop time performance as the number ofcycles increases for the Conventional-1 material as compared to theExamples B, D and E materials.

FIG. 10 is a graph showing high energy friction test cycles for aconventional material impregnated with a phenolic resin (Conventional-1)as compared to fibrous base material impregnated with an epoxy-phenolicresin (Example D).

FIG. 11 is a graph showing the high speed durability test at 7,000 rpm,0.3 LPM oil flow 1.5 kg-cm-sec² inertia showing the dynamic coefficientof friction as the number of cycles increases for a fibrous basefriction material impregnated with an epoxy-phenolic resin (Example D)and the Conventional-1 material and a conventional friction materialimpregnated with a phenolic resin (Conventional-2).

FIG. 12 is a graph showing the high energy durability test at 3,600 rpm,8.0 kg/cm² lining pressure, 5.0 kg-cm-sec² inertia showing the dynamiccoefficient of friction as the number of cycles increases for a ExampleD and the two conventional materials, Conventional-1 and Conventional-2.

FIG. 13 is a graph showing the engine dynamometer 4-3 down shiftdurability test, 2,000 cc IG/FE engine, 5,800 rpm showing the shift timein seconds for the 4-3 down shift engagements for the Example D and thetwo conventional friction materials, Conventional 1 and Conventional-2.

FIG. 14 is a graph comparing the shear strength (psi) for a fibrous basematerial impregnated with an epoxy-phenolic resin (Example E) and aconventional material (Conventional-2).

FIG. 15 is a graph showing the pore size (in microns) for a fibrous basematerial impregnated with an epoxy-phenolic resin (Example E) and aconventional material (Conventional-2).

FIG. 16 is a graph comparing the liquid permeability (cm² ×10⁻³) for afibrous base material impregnated with an epoxy-phenolic resin (ExampleE) and a conventional material (Conventional-2).

FIG. 17 is a graph showing the speed, torque, temperature and appliedpressure for Example E at an interface temperature of about 695° F. for500 cycles.

FIG. 18 is a graph showing the speed, torque, temperature and appliedpressure for Example E at an interface temperature of about 896° F. for10,500 cycles.

FIG. 19 is a graph showing the mid point dynamic coefficient of frictionfor Example E as the number of cycles increases.

FIG. 20 is a graph showing the high speed durability showing the midpoint coefficient of friction as the number of cycles increases forExamples C and E, as compared to the Conventional-1 material.

FIG. 21 is a graph showing a high speed durability at 6,000 rpm using anExxon 1975 fluid showing the static to dynamic coefficient of frictionratio as the number of cycles increases for Examples C and E, ascompared to the Conventional-1 material.

FIG. 22 is a graph showing a high speed durability test at 6,000 rpmusing an automatic transmission fluid JWS2318K showing the coefficientof friction as the number of cycles increases for Examples C, D and F,as compared to the Conventional-1 material.

FIG. 23 is a scanning electron microphotograph of a fibrous basematerial comprising about 45% less fibrillated aramid fibers (CSF about450-500), about 23% synthetic graphite, about 27% diatomaceous earth,and about 5% aramid fiber pulp (Example L).

FIG. 24 is a scanning electron microphotograph of a fibrous basematerial comprising about 45% less fibrillated aramid fibers (CSF about580-640), about 23% synthetic graphite, about 27% diatomaceous earth andabout 5% aramid fiber pulp (Example K).

BEST MODE OF CARRYING OUT THE INVENTION

Various resins useful in the present invention include phenolic resinsand phenolic-based resins. It is to be understood that variousphenolic-based resins which include in the resin blend other modifyingingredients, such as epoxy, butadiene, silicone, tung oil, benzene,cashew nut oil and the like, are contemplated as being useful with thepresent invention. In the phenolic-modified resins, the phenolic resinis generally present at about 50% or greater by weight (excluding anysolvents present) of the resin blend. However, it has been found thatfriction materials, in certain embodiments, can be improved when theimpregnant resin blend contains about 5 to about 80%, by weight, and forcertain purposes, about 15 to about 55%, and in certain embodimentsabout 15 to about 25%, by weight, of silicone resin based on the weightof the silicone-phenolic mixture (excluding solvents and otherprocessing acids).

Silicone resins useful in the present invention include, for example,thermal curing silicone sealants and silicone rubbers. Various siliconeresins are useful with the present invention. One resin, in particular,comprises xylene and acetylacetone (2,4-pentanedione). The siliconeresin has a boiling point of about 362° F. (183° C.), vapor pressure at68° F. ram, Hg: 21, vapor density (air=1) of 4.8, negligible solubilityin water, specific gravity of about 1.09, percent volatile, by weight,5% evaporation rate (ether=1), less than 0.1, flash point about 149° F.(65° C.) using the Pensky-Martens method. It is to be understood thatother silicone resins can be utilized with the present invention. Otheruseful resin blends include, for example, a suitable phenolic resincomprises (% by wt.): about 55 to about 60% phenolic resin; about 20 toabout 25% ethyl alcohol; about 10 to about 14% phenol; about 3 to about4% methyl alcohol; about 0.3 to about 0.8% formaldehyde; and, about 10to about 20% water. Another suitable phenolic-based resin comprises (%by wt.): about 50 to about 55% phenol/formaldehyde resin; about 0.5%formaldehyde; about 11% phenol; about 30 to about 35% isopropanol; and,about 1 to about 5% water.

It has also been found that another useful resin is an epoxy modifiedphenolic resin which contains about 5 to about 25 percent, by weight,and preferably about 10 to about 15 percent, by weight, of an epoxycompound with the remainder (excluding solvents and other processingaids) phenolic resin. The epoxy-phenolic resin compound provides, incertain embodiments, higher heat resistance to the friction materialthan the phenolic resin alone.

It further contemplated that other ingredients and processing aids knownto be useful in both preparing resin blends and in preparingimpregnating fibrous-based materials can be included in the frictionmaterials.

For the embodiments where a phenolic resin and silicone resin are used,no new compound is formed when the silicone resin and phenolic resin areblended together. Table 1 shows the prominent FT-IR peaks in wavenumbers for a cured silicone resin, a cured phenolic resin, and about50/50 blend of silicone resin and phenolic resin which has been cured.As can be seen, no new peaks occur in the 50/50 silicone-phenolic blend,and the peaks that are present reflect the presence of both the siliconeresin and the phenolic resin. Thus, it is shown that the resins cureseparately and that no new compound is formed.

                  TABLE 1                                                         ______________________________________                                        PROMINENT FT-IR PEAKS                                                         IN WAVENUMBERS                                                                SILICONE RESIN                                                                              PHENOLIC RESIN                                                                             50/50 BLEND                                        ______________________________________                                        --            3364         3366                                               2966          --           2964                                               --            1510         1510                                               --            1479         1481                                               1412          --           1410                                               1271          --           1261                                                798          --            800                                                767          --            769                                               ______________________________________                                    

Both the silicone resin and the phenolic resin are present in solventswhich are compatible to each other. These resins are mixed together (inpreferred embodiments) to form a homogeneous blend and then used toimpregnate a fibrous base material. There is not the same effect if afibrous base material is impregnated with a phenolic resin and then asilicone resin is added thereafter or vice versa. There is also adifference between a mixture of a silicone-phenolic resin solution, andemulsions of silicone resin powder and/or phenolic resin powder. Whensilicone resins and phenolic resins are in solution they are not curedat all. In contrast, the powder particles of silicone resins andphenolic resins are partially cured. The partial cure of the siliconeresins and the phenolic resins inhibits a good impregnation of thefibrous base material.

Therefore, according to one aspect of the present invention, the fibrousbase material is impregnated with a blend of a silicone resin in asolvent which is compatible with the phenolic resin and its solvent. Inone embodiment, isopropanol has been found to be an especially suitablesolvent. It is to be understood, however, that various other suitablesolvents, such as ethanol, methyl-ethyl ketone, butanol, isopropanol,toluene and the like, can be utilized in the practice of this invention.According to the present invention, the presence of a silicone resin,when blended with a phenolic resin and used to impregnate a fibrous basematerial, causes the resulting friction materials to be more elasticthan fibrous base materials impregnated only with a phenolic resin. Whenpressures are applied to the silicone-phenolic resin blended impregnatedfriction material of the present invention, there is a more evendistribution of pressure which, in turn, reduces the likelihood ofuneven lining wear. After the silicone resin and phenolic resin aremixed together, the mixture is used to impregnate a fibrous basematerial.

Various methods for impregnating materials can be practiced with thepresent invention. The fibrous base material is impregnated with thephenolic or modified phenolic resin, preferably so that the impregnatingresin material comprises about 45 to about 65 parts, by weight, per 100parts, by weight, of the friction material. After the fibrous basematerial has been impregnated with the resin, the impregnated fibrousbase material is heated to a desired temperature for a predeterminedlength of time to form the friction material. The heating cures thephenolic resin at a temperature of about 300° F. When other resins arepresent, such as a silicone resin, the heating cures the silicone resinat a temperature of about 400° F. Thereafter, the impregnated and curedfriction material is adhered to the desired substrate by suitable means.

Another aspect of the present invention relates to a fibrous basematerial comprising less fibrillated aramid fibers, synthetic graphiteand at least one filler material, which are combined to form apaper-like fibrous base material. It is to be understood that variousmethods of forming fibrous base materials are contemplated as beinguseful in preparing the fibrous base material of the present invention.It has been found by the inventors herein that the use of lessfibrillated aramid fibers and synthetic graphite in a fibrous basematerial improves the friction material's ability to withstand hightemperatures.

While various friction lining materials disclose the use of aramidfibers, it has not been known until the present invention to provide afriction material comprising less fibrillated aramid fibers whichgenerally have few fibrils attached to a core fiber. The use of the lessfibrillated aramid fibers provides a friction material having a moreporous structure; i.e., there are more and larger pores than if atypical fibrillated aramid fiber is used, The porous structure isgenerally defined by the pore size and liquid permeability. In apreferred embodiment, the fibrous base material defines pores ranging inmean average size from about 2.0 to about 15 microns in diameter. Thelength of the less fibrillated fiber ranges from about 0.5 to about 6 mmand has a Canadian Standard Freeness (CSF) of greater than about 450 andin certain embodiments, about 500 to about 550 and in other certainembodiments, about 580-640 and most preferably about 620-640. Incontrast, more fibrillated fibers, such as aramid pulp, have a freenessof about 285-290.

The "Canadian Standard Freeness" (T227 om-85) means that the degree offibrillation of fibers can be described as the measurement of freenessof the fibers. The CSF test is an empirical procedure which gives anarbitrary measure of the rate at which suspension of three grams offibers in one liter of water may be drained. Therefore, the lessfibrillated aramid fibers have higher freeness or higher rate ofdrainage of fluid from the friction material than other aramid fibers orpulp. It has now been surprisingly found that friction materialscomprising the aramid fibers having a CSF ranging from about 530-650,preferably about 580-640, and most preferably about 620-640, providesuperior friction performance and have better material properties thanfriction materials containing conventionally more fibrillated aramidfibers. It has surprisingly been found that the longer fiber length,together with the high Canadian freeness, provide a friction materialwith high strength, high porosity and good wear resistance. As shown inthe examples below, high energy tests conducted with materialscontaining, for example, the less fibrillated aramid fibers (CSF about580-640), have good long-term durability and stable coefficients offriction.

The more porous the structure of the friction material, the moreefficient is the heat dissipation. The oil flow in and out of thefriction material during engagement of the friction material during useoccurs more rapidly when the friction material is porous.

It has further been discovered that the less fibrillated fibers,synthetic graphite and filler improve the pore structure of the fibrousbase material so that there are more porous openings throughout thefibrous base material. The increased porosity also increases theelasticity of the friction material. A lower degree of fibrillation ofthe less fibrillated aramid fibers results in a friction material havinga more porous structure.

It has not been known until the present invention to include syntheticgraphite in a fibrous base material comprising less fibrillated aramidfibers. The use of synthetic graphite in the fibrous base materialprovides a more three dimensional structure to the fibrous base materialthan other types of graphite material. The synthetic graphite is made bygraphitization of a raw stock material such as petroleum coke and a coaltar pitch binder. The raw materials are mixed and heated to temperaturesof about 2,800° to about 3,000° C. in special graphitizing furnaceswhich convert the baked carbon body into a polycrystaline graphitearticle. The synthetic graphite (which has high thermal conductivity)provides the friction material with the ability to dissipate heat morerapidly than other types of graphite. In certain embodiments, it ispreferred that the size and geometry of the synthetic graphite be in theabout 20 to about 50 micron size range. In these certain embodiments, ithas been discovered that if the graphite particle size is too large ortoo small, there is not the optimum three-dimensional structure andconsequently the heat resistance is not as optimum.

Various fillers are also used in the fibrous base material of thepresent invention. In particular, silica fillers, such as diatomaceousearth, are useful. However, it is contemplated that other types offillers are suitable for use in the present invention and that thechoice filler depends on the particular requirements of the frictionmaterial. Other ingredients can be added to the fibrous base material ofthe present invention, including for example, cotton fibers which can beadded to give the fibrous material higher coefficients of friction. Incertain embodiments, about 0 to about 20%, and in certain embodimentsabout 5 to about 15%, other filler such as aramid pulp and/or aramidfloc can also be added to the fibrous base material.

One example of a formulation for a fibrous base material comprises about10 to about 50%, by weight, of a less fibrillated aramid fiber; about 10to about 35%, by weight, of a synthetic graphite; and, about 20 to about45%, by weight, of a filler material. In certain embodiments, oneparticular formulation has found to be useful comprises about 45 toabout 50%, by weight, less fibrillated aramid fibers: about 15 to about25%, by weight, synthetic graphite; and, about 20 to about 30%, byweight, filler. Another useful formulation comprises about 20 to about30% less fibrillated aramid fibers, about 15 to about 25% syntheticgraphite, about 20 to about 30% filler material, and optionally about 0to about 40% cotton fibers. In further embodiments, the cotton fiberscan be present at about 20 to about 40%, by weight, or about 25 to about35%, by weight.

The following examples provide further evidence that the fibrous basematerial and friction material of the present invention are animprovement over the conventional friction material. Various preferredembodiments of the invention are described in the following examples,which however, are not intended to limit the scope of the invention.

Examples A and B both are a fibrous base material comprising about, inpercent, in weight, about 45% less fibrillated aramid fibers, about 23%synthetic graphite, about 27% diatomaceous earth filler, and about 5%optional filler comprising aramid pulp. Example A is impregnated with aphenolic material and Example B is impregnated with a silicone-phenolicresin blend comprising about 20% silicone and about 80% phenolic resins.

Example C is a fibrous base material comprising in percent, by weight,about 35% less fibrillated aramid fibers, about 25% synthetic graphite,about 25% diatomaceous earth filler material, and other optional fillersof about 5% aramid pulp and about 10% aramid floc, and impregnated witha silicone-phenolic resin blend.

Example D is a fibrous base material comprising in percent, by weight,about 25% less fibrillated aramid fibers, about 20% synthetic graphite,about 25% diatomaceous earth, and about 30% cotton fibers andimpregnated with a first epoxy-phenolic resin blend comprising about 10%epoxy and about 90% phenolic resins.

Example E is a fibrous base material comprising about 25% lessfibrillated aramid fibers, about 20% synthetic graphite, about 25%diatomaceous earth, and about 30% cotton fibers and impregnated with asecond epoxy-phenolic resin.

Example F is a fibrous base material comprising, in percent, by weight,about 25% less fibrilated aramid fibers, about 20% synthetic graphite,about 25% diatomaceous earth, and about 30% cotton fibers andimpregnated with the second epoxy-phenolic resin blend

EXAMPLE 1

FIG. 1A, shows a scanning electron microscopic (SEM) photograph ofExample C which indicates that a thin film of silicone resin formsbetween the fibers during impregnation. Example C has an increased poresize over friction materials impregnated with either a silicone resin orphenolic resin alone, Since the silicone resins and phenolic resins cureat different temperatures, the phenolic resin cures first while thesilicone resin cures later. A thin film of silicone resins formedbetween the fibers during cure. This thin film of silicone resin betweenthe fibers is thought to contribute to the high friction stability ofthe friction material. The film of silicone resin slows down thedeterioration of the friction material and allows the friction materialto have a high heat resistance at high temperatures.

The SEM photographs shown in FIG. 1A show a much larger pore structurethan for the phenolic resin-impregnated friction material, aconventional material (Conventional-1) which contains no lessfibrillated aramid fibers and no synthetic graphite, shown in FIG. 1B,

As seen in FIG. 1A, the blend of silicone and phenolic resins results ina fiber-resin interaction which creates a flexible and open fibernetwork. Up to about a 50% larger pore size has been seen with thephenolic-silicone blend impregnated friction material than over phenolicresin impregnated friction material alone. In certain embodiments, themean pore size ranges from about 2.5 to about 4 microns in diameter andthe friction material had readily available air voids of at least about50% and in certain embodiments at least about 60% or higher.

EXAMPLE 2

The capillary flow and permeability tests are shown in Table 2 below forExamples B, D, E and a comparative material having natural graphite butno synthetic graphite. The higher mean flow pore diameter and Darcy'spermeability indicate that the friction material is more likely to runcooler or with less heat generated in a transmission due to betterautomatic transmission fluid flow of material throughout the porousstructure of the friction material. During operation of a transmissionsystem, oil deposits on the surface of a friction material tend todevelop over time due to a breakdown of the automatic transmissionfluid, especially at high temperatures. The oil deposits on the fibersdecrease the pore openings. Therefore, when a friction materialinitially starts with larger pores, there are more open pores remainingduring the useful life of the friction material. In addition, thesilicone resin, due its elastic characteristics, allows the fibers inthe friction lining to have a more open structure.

                  TABLE 2                                                         ______________________________________                                        CAPILLARY FLOW AND PERMEABILITY                                               Darcy's       Mean Flow    Sample Thickness                                   Permeability  Pore Diameter                                                                              Inches, cm                                         ______________________________________                                        Ex. B   2.0 × 10                                                                          2.77 microns 0.021 0.05334                                  Ex. D   1.0 × 10.sup.-2                                                                   2.85 microns 0.016 0.04191                                  Ex. E   1.0 × 10.sup.-2                                                                   2.34 microns 0.017 0.04318                                  Compar. 5.1 × 10.sup.-3                                                                   1.77 microns 0.019 0.04826                                  ______________________________________                                    

EXAMPLE 3

Glaze analysis of the scanning electron microscopic photographs showsthat the silicone-phenolic resin blend has a slight fiber compression onthe surface while the phenolic resin alone has a pronounced fibercompression on the surface for unused plates. Further, as seen in Table3, in used plates, there are open pores remaining in a silicone-phenolicresin blend while there are very few pores open in the phenolic resinmaterial alone.

                  TABLE 3                                                         ______________________________________                                        GLAZE ANALYSIS                                                                SCANNING ELECTRON MICROSCOPY                                                  Example C          Conventional Material - 1                                  ______________________________________                                        UNUSED PLATES                                                                 * Slight fiber compression                                                                       * Pronounced fiber                                           on surface         compression on surface                                   * No fiber compression                                                                           * No fiber compression                                       internally         internally                                               * Resin forms a film between                                                                     * Resin only coats fibers                                    fibers                                                                      USED PLATES                                                                   * Surface Glazes   * Surface glazes                                           * Open pores       * Very few open pores                                      ______________________________________                                    

EXAMPLE 4

Previously, unreacted silicone resins have not been acceptable for usein a friction material since the silicone resin has low strength.However, it has now been found that the shear strength of thesilicone-phenolic resin blends is remarkably higher than for phenolicresins alone. The tensile shear test was run on the Instron tensiletester. A modified lap shear configuration was used with a 2 square incharea of friction material bonded on both side to steel plates. Thisassembly was then pulled until the paper sheared. The values in Table 4below indicate the internal shear strength of the paper under dryconditions at room temperature for Examples B, E and D.

The higher the shear strength, the better mechanical strength thefriction material has which means that more pressure is needed to shearthe friction lining.

                  TABLE 4                                                         ______________________________________                                                 Shear Strength PSI                                                   ______________________________________                                        Ex. B      382.5                                                                         382.5                                                              Ex. E      325.0                                                                         290.0                                                              Ex. D      352.5                                                                         385.0                                                              ______________________________________                                    

EXAMPLE 5

The silicone-phenolic resin blend provides at least about a 50% increasein the "burn off" temperature of the friction material. This highfriction stability is an advantage over the currently available frictionmaterials. A thermal gravimetric analysis (TGA) shown in FIG. 2, whereinthe TGA curve shifts to higher temperatures, indicates increased heatresistance of the silicone-phenolic resin blend over the phenolicmaterial.

Both Examples A and B have improved heat resistance over conventionalmaterials and Example B is especially suitable for end-use frictionmaterial applications where heat resistance is a critical criterion.

FIGS. 3 and 4 compare the TGA graphs shown in FIG. 2, and the change inderivative weight (%/°C.) for the phenolic resin, Example A in FIG. 2(FIG. 3) and the silicone-phenolic blend, Example B in FIG. 2 (FIG. 4).The percent change in weight for the phenolic resin was 69.41% while thepercent change in weight for the silicone-phenolic blend was 61.87%. Asseen from FIGS. 3-4, the more rapid the weight loss, the less heatresistance the friction material possess.

EXAMPLE 6

FIG. 5 shows the stop time as the number of cycles increases for variousmaterials: Example C, D and F as compared to the Conventional-1 materialimpregnated with a butadiene-phenolic resin. The fibrous materials(Examples C, D and F) maintained a relatively uniform stop time, whilethe stop time for the conventional material rapidly rose to unacceptablelevels.

The ratio between the static coefficient of friction and the dynamiccoefficient of friction as the number of cycles increases was comparedfor Examples C, D and F and for the Conventional-1 material. As can beseen in FIG. 6, the fibrous base material impregnated withsilicone-phenolic blend material (Example C) performs consistentlybetter than the conventional material while the fibrous base materialimpregnated with epoxy-phenolic resins (Examples D and F) performedcomparatively well.

The dynamic coefficient of friction as the number of cycles increase wascompared for Examples C, D and F and for the conventional material(Conventional-1). FIG. 7 shows the dynamic coefficient of friction forthe friction materials (Examples C, D and F) remain relatively steady asthe number the cycles increased. Thus, the fibrous base materialsperform much better at a high speed than the conventional material. Itis important to note that there is no "fall off" of the coefficient offriction as the number of cycles increases for the fibrous basematerials.

A materials evaluation for a clutch run at 6,600 rpm (65 m/sec.),limited lubrication of 0.2 gpm was conducted for Examples B, D and E andfor the Conventional-1 material. The dynamic mid point coefficientgraphs of FIG. 8 shows that the conventional material was totallyunacceptable while the friction Examples B, D and E materials have arelatively steady coefficient of friction indicating that the system wasvery stable. As can be seen in FIG. 9, the stop time for theconventional material rapidly increased to unacceptable levels while thefriction materials (Examples B, D and E) maintained an acceptably shortstop time of about 0.52 to about 0.58 seconds throughout the test.

EXAMPLE 7

In certain embodiments, it is preferred that the target pick up of resinby the friction material range from about 40 to about 65%, and, incertain embodiments, about 60 to at least 65%, by weight, totalsilicone-phenolic resin. After the fibrous base material is impregnatedwith the resin, the fibrous base material is cured for a period of time(in certain embodiments for about 1/2 hour) at temperatures rangingbetween 300°-400° C. to cure the resin binder in the friction material.The final thickness of the friction material depends on the initialthickness of the fibrous base material and, in certain embodiments,preferably ranges from about 0.014" to about 0.040".

In Table 5 below, a friction material comprising the fibrous basematerial impregnated with about 60% resin pick up (P.U.) of asilicone-phenolic resin (Example C) was compared to a friction materialcomprising the same fibrous base material as in Example C butimpregnated with a phenolic resin with about 60% resin pick up (P.U.)(Example C-1) and to the Conventional-1 material impregnated with aphenolic resin with about 49% P.U. (Conventional-1). Assembly or coreplates were lined with friction materials impregnated with the testedresins to form a pack for testing. The dynamic coefficient of frictionremained steady (with a loss of only 5%) as the number of cyclesincreased for the silicone-phenolic resin friction materials. There wasno lining wear on the plates using the silicone-phenolic resin frictionmaterial. The lining condition of the silicone-phenolic resin blendfriction material remained good without breakouts, abrasion, or glazingoccurring. Further, the steel condition of the separator plates show nohot spots for the silicone-phenolic blend friction materials.

                  TABLE 5                                                         ______________________________________                                        EFFECT OF RESIN CHANGE                                                                    CONV'L - 1  EX. C-1   EXAMPLE C                                   TEST RESIN %                                                                              49% P.U.    60% P.U.  60% P.U.                                    ______________________________________                                        LINING THICKNESS                                                                          0.016"      0.016"    0.016"                                      CYCLES                                                                        MID. DYNAMIC                                                                    75        0.135       0.134     0.134                                       3,000       0.121       0.123     0.130                                       6,000       0.118       0.113     0.127                                       STOP TIME SEC.                                                                  75        0.804       0.799     0.796                                       3,000       0.880       0.858     0.817                                       6,000       0.904       0.910     0.835                                       TORQUE CURVE                                                                              Decrease    Decrease  Decrease                                    SHAPING                                                                       LINING LOSS 0.0027"     0.0009"   No Loss                                     PER PLATE                                                                     LINING CONDITION                                                                          Breakouts Heavy                                                                           Abrasion  Good                                                    Glaze       Glaze                                                 STEEL CONDITION                                                                           Distinct Hot                                                                              Few Small Light Heat                                              Spots       Hot Spots Stains                                      ______________________________________                                    

EXAMPLE 8

Table 6 below shows compression/relaxation studies done on an MTSmachine. This test reports the effect on paper caliper caused byrepeatedly pressing on a sample and releasing the sample through aseries of different pressures. These readings provide an indication ofthe internal resistance to set or compacting due to pressing. TheExample B material shows a greater elasticity than the comparativeexample described in Table 2 above. This greater elasticity allows formore uniform heat dissipation during use of the friction material sincethe fluid in the transmission or brake can rapidly move through theporous structure. Further, the increased elasticity provides moreuniform pressure or even pressure distribution on the friction materialsuch that uneven lining wear or separator plate "hot spots" areeliminated.

                  TABLE 6                                                         ______________________________________                                        LOAD VS DEFLECTION                                                            Compression/compression Set                                                   Pressure                                                                      Psi           Example B    Compar.                                            ______________________________________                                         15 psi       .0000"/1 in. .0000"/1 in.                                                     .0000"       .0000"                                              50 psi       .0180"/1 in. .0104"/1 in.                                                     .0066"       .0034"                                             100 psi       .0348"/1 in. .0233"/1 in.                                                     .0083"       .0049"                                             200 psi       .0600"/1 in. .0419"/1 in.                                                     .0115"       .0070"                                             300 psi       .0805"/1 in. .0565"/1 in.                                                     .0123"       .0076"                                             400 psi       .0963"/1 in. .0658"/1 in.                                                     .0159"       .0070"                                             500 psi       .1112"/1 in. .0742"/1 in.                                                     .0188"       .0079"                                             709 psi       .1369"/1 in. .0939"/1 in.                                                     .0232"       .0111"                                             900 psi       .1533"/1 in. .1090"/1 in.                                                     .0242"       .0134"                                             1100 psi      .1703"/1 in. .1248"/1 in.                                                     .0267"       .0152"                                             1300 psi      .1922"/1 in. .1419"/1 in.                                                     .0324"       .0190"                                             1500 psi      .2179"/1 in. .1630"/1 in.                                                     .0404"       .0248"                                             ______________________________________                                    

EXAMPLE 9

A friction material comprising less fibrillated aramid fibers andsynthetic graphite impregnated with an epoxy modified phenolic resin(Example D) and was compared to the conventional material(Conventional-1). A high speed friction cycles test is shown in FIG. 10,comparing the stroking test life and high energy friction test cycles.The friction material of the present invention performs better in allaspects than the conventional friction material.

FIG. 11 shows the results of a high speed durability test at 7,000 rpm,0.3 LPM oil flow with 1.5 kg-cm-sec² inertia. As the number of cyclesincreases, the dynamic coefficient of friction remained relativelyuniform for the friction material (Example D) while one conventionalmaterial (Conventional-2) failed at the beginning of the test and theperformance of another impregnated material impregnated with aphenolic-based resin (Conventional-1) rapidly fell off after about 3,000cycles.

FIG. 12 shows the results of a high energy durability test at 3,600 rpm,8.0 kg/cm² lining pressure at 5.0 kg-cm-sec² inertia. The dynamiccoefficient of friction for the friction material (Example D) remainedremarkably steady throughout the entire durability test. In comparison,the conventional materials failed at an unacceptably short cycle ofusage life.

FIG. 13 shows the results of an engine dynamometer 4-3 down shiftdurability test for a 2,000 cc IG/FE engine at 5,800 rpm. As can beseen, the shift time in seconds for the 4-3 down shift engagements forthe friction material (Example D) remain relatively constant through atleast 40,000 down shift engagements. The conventional materials hadrapid increases in shift time at low shift engagement cycles.

EXAMPLE 10

The friction material of the present invention has high durability andhigh delamination resistance. The shear strength (psi) for the frictionmaterial of the present invention is greater than for the conventionalmaterials, as seen in FIG. 14. The use of the less fibrillated fibersand the resulting pore structure of the friction material providesincreased thermal resistance to the friction material. The fibergeometry not only provides increased thermal resistance, but alsoprovides delamination resistance and squeal resistance. The presence ofthe synthetic graphite particles and at least one filler material aidsin increasing the thermal resistance, maintaining a steady coefficientof friction, and increasing the squeal resistance.

EXAMPLE 11

The average pore size for the friction material of the present inventionas compared to the pore size of a conventionally resin impregnatedfriction material is shown in FIG. 15. The average pore size of thefriction lining of the present invention ranges from about 2.0 to about15 microns and is between about 20 to about 100% larger than for theconventional friction materials.

EXAMPLE 12

The liquid permeability for the friction material of the presentinvention was compared to a conventional material impregnated with aphenolic resin (Conventional-2). As seen in FIG. 16, the frictionmaterial of the present invention has about a 20% increase in liquidpermeability over the conventional materials.

EXAMPLE 13

FIG. 17 shows a friction material (Example D) comprising about 0.02"lining with about 44% pick up of a phenolic-epoxy resin at about 380° F.after 1/2 hour cure at an interface temperature of about 695° F. FIG. 17compares the speed, torque, temperature and applied pressure of thematerial run at 500 cycles showing the high friction stability of thefriction material of the present invention.

FIG. 18 shows the high friction stability of the friction material(Example D) comprising a 0.02" lining with about a 44% resin pick up ofanother phenolic-based resin cured at 380° F. for 1/2 hour, at aninterface temperature of 895° F. FIG. 18 shows the speed, torque,temperature and applied pressure of the material run for 10,500 cycles.

Table 7 below shows the mid point coefficient of friction for thefriction material (Example D) shown in FIGS. 17 and 18. The coefficientof friction remains relatively steady as the cycles increase, thusshowing the high friction stability of the friction material. Also, asshown in FIG. 19, the mid point dynamic coefficient of friction for theabove described friction materials in FIGS. 17 and 18 show that as thenumber of cycles increased, the mid point coefficient of frictionremained relatively steady. The torque curve shape shows that thefriction material of the present invention is especially useful in highspeed, high energy and high temperature applications. The total loss offriction material was only about 0.0077 inches and a loss per plate wasabout 0.0039 inches. The friction material showed a medium glaze and theseparator was only light heat stained, thus indicating a high qualityfriction material which is stable over a long period of time.

                  TABLE 7                                                         ______________________________________                                        Example D                                                                                  MID                                                              CYCLES       COEFFICIENT                                                      ______________________________________                                         50          .132                                                             100          .136                                                             300          .135                                                             500          .131                                                             550          .131                                                             600          .129                                                             900          .124                                                             1200         .122                                                             1500         .121                                                             2500         .121                                                             4500         .122                                                             6500         .121                                                             8500         .123                                                             10500        .126                                                             ______________________________________                                    

EXAMPLE 14

FIG. 20 shows a high speed durability test comparing a conventionalphenolic-based material impregnating a conventional friction lining toone embodiment of the friction material of the present materialimpregnated with a silicone-phenolic resin blend material (Example C)and another embodiment of the friction material of the present inventionimpregnated with a phenolic-epoxy resin material (Example D). Both thefriction materials of the present invention had more stable mid pointcoefficients of friction than the conventional friction material.

A high speed durability test run at 6,000 rpm was conducted comparingthe static to dynamic (S/D) coefficient of friction over a number ofincreasing cycles. As seen in FIG. 21, the conventional phenolicimpregnated friction material was compared to a silicone-phenolicimpregnated friction material of the present invention (Example C) andepoxy-phenolic impregnated friction material (Example E) of the presentinvention. The materials of the present invention have favorable staticto dynamic coefficient of friction ratios to the conventional material.

The coefficient of friction as cycles increase at 6,000 rpm was testedfor three samples of the fibrous base material of the present invention,each impregnated with a resin as follows: phenolic-epoxy impregnatedresin at a 0.016 inch thin fibrous base material (Example D),phenolic-based resin impregnated at 0.020 inch thick fibrous basematerial (Example F), and a silicone-phenolic resin (Example C). As seenin FIG. 22, these fibrous base materials impregnated with the variousresins compared favorably to a conventional friction material, whichperformed more poorly than each of the friction materials of the presentinvention.

The following further examples provide additional evidence that afibrous base material comprising at least one type of aramid fiberhaving a CSF of greater than about 530 preferably about 580-640 and mostpreferably about 620-640 is especially useful in friction materials.Such fibrous base materials are an improvement over other types offibrous base materials. Various comparative examples and variouspreferred embodiments are described in the following examples, whichhowever, are not intended to limit the scope of the invention. Each ofthe following examples, Comparative 3, Comparative 4 and Examples G, H,I and J is a formulation which is a fibrous base material comprising, inpercent, by weight, about 20% synthetic graphite, about 25% diatomaceousearth, about 30% cotton fibers, and varying types of fibers:

Comparative Ex. 3 about 25% epoxy coated aramid fibers (1 mm in length);

Comparative Ex. 4 about 25% epoxy coated aramid fibers (3 mm in length);

Example G about 25% aramid fibers--CSF about 540;

Example H about 25% aramid fibers--CSF about 585;

Example I about 25% aramid fibers--CSF about 620-640; and

Example J about 25% aramid fibers--CSF about 450-500.

EXAMPLE 15

The mean pore diameter for Comparative 3, Comparative 4 and Examples G,H and I are shown in Table 8 below for both resin saturated fibrous basematerials and for raw papers (unsaturated).

The higher mean flow pore diameter indicates that the friction materialis more likely to have lower interface temperature with more efficientheat dissipation in a transmission due to better automatic transmissionfluid flow of material throughout the porous structure of the frictionmaterial. During operation of a transmission system, oil deposits on thesurface of a friction material tend to develop over time due to abreakdown of automatic transmission fluid, especially at hightemperatures. The oil deposits on the fibers decrease the pore openings.Therefore, when a friction material initially starts with larger pores,there are more open pores remaining during the useful life of thefriction material. It is noted that Example I (comprising lessfibrillated aramid fibers (CSF about 620-640)) has especially desirablemean pore diameters.

                  TABLE 8                                                         ______________________________________                                                      Mean                                                                   Material                                                                             Pore                                                                   ID     Dia. (μm)                                                    ______________________________________                                               Compar. 3                                                                            15.1                                                                   Compar. 4                                                                            23.9                                                                   Ex. G  4.3                                                                    Ex. H  5.4                                                                    Ex. I  7.0                                                             RAW PAPER                                                                            Compar. 3                                                                            25.9                                                                   Compar. 4                                                                            26.3                                                                   Ex. G  5.5                                                                    Ex. H  6.0                                                                    Ex. I  7.8                                                             ______________________________________                                    

EXAMPLE 16

Table 9 below indicates the compression, compression set and shearstrength values for the Comparative 3, Comparative 4 and Examples G, Hand I. it is to be especially noted that Examples G, H and I haveacceptable compression and compression set values and further that theshear strength is much greater than Comparatives 3 and 4.

                  TABLE 9                                                         ______________________________________                                        Friction                        Shear                                         Material Comp.         Comp. Set                                                                              Strength                                      ID       in./in.       in./in.  psi                                           ______________________________________                                                 100 psi       100 psi  A                                                      300 psi       300 psi  B                                                      700 psi       700 psi  C                                                      1500 psi      1500 psi Avg.                                          Compar. 3                                                                              0.0608        0.0141   128                                                    0.1222        0.0232   126                                                    0.1847        0.0426   126                                                    0.2999        0.1049   127                                           Compar. 4                                                                              0.0771        0.0188    83                                                    0.1448        0.0309    89                                                    0.2078        0.0488    90                                                    0.2955        0.0821    87                                           Ex. G    0.0157        -0.0005  364                                                    0.0475        0.0002   357                                                    0.0943        0.0108   341                                                    0.1946        0.0510   354                                           Ex. H    0.0206        0.0017   313                                                    0.0528        0.0030   325                                                    0.0978        0.0118   317                                                    0.1721        0.0414   318                                           Ex. I    0.0196        0.0000   332                                                    0.0546        0.0015   349                                                    0.1119        0.0110   336                                                    0.2321        0.0482   339                                           ______________________________________                                    

EXAMPLE 17

Table 10 provides a summary of test procedure conditions for the highspeed durability tests 5004C and 5004A and the break-in characteristictest 5004D, the high energy durability tests 5003A and 5030C, and theμ-v-p-t characteristic test 5010A for the materials shown in Examples18-23 below.

                                      TABLE 10                                    __________________________________________________________________________                               Break-in                                                  High Speed Durability Test                                                                        Characteristic                                     Test Procedure                                                                       5004C     5004A     5004D                                              __________________________________________________________________________    Level  Level                                                                              A & C                                                                              Level                                                                              A & C                                                                              Level                                                                              A                                             Cycles 50   cycles                                                                             ←    200  cycles                                        Speed  3700 rpm  ←    ←                                             Inertia                                                                              2.17 kgcm.sec.sup.2                                                                     ←    ←                                             Pressure                                                                             137.8                                                                              KPa  ←    ←                                             Temperature                                                                          100-100°                                                                    C.   ←    ←                                             Oil flow                                                                             0.757                                                                              lpm  ←    ←                                             Kinetic energy                                                                       15122                                                                              Joule                                                                              ←    ←                                             Level  Level                                                                              B    Level                                                                              B    --                                                 Cycles 5009 cycles                                                                             2000 cycles                                                                             --                                                 Speed  6200 rpm  ←    --                                                 Inertia                                                                              1.70 kgcmsec.sup.2                                                                      ←    --                                                 Pressure                                                                             --        --        --                                                 Stop Time                                                                            *0.8 sec. ←    --                                                 Temperature                                                                          115-120°                                                                    C.   110-110°                                                                    C.   --                                                 Oil flow                                                                             0.787                                                                              lpm  ←    --                                                 Kinetic energy                                                                       35720                                                                              Joule                                                                              ←    --                                                 Power density                                                                        1.98 W/mm.sup.2                                                                         ←    --                                                 __________________________________________________________________________                               Break-in                                                  High Speed Durability Test                                                                        Characteristic                                     Test Procedure                                                                       5003C     5030C     5010A                                              __________________________________________________________________________    Level  Level                                                                              A & C                                                                              Level                                                                              A & C                                                                              Level                                                                              A                                             Cycles 50   cycles                                                                             ←    200  cycles                                        Speed  3600 rpm  ←    800  rpm                                           Inertia                                                                              1.70 kgcmsec.sup.2                                                                      ←    3.553                                                                              kgcmsec.sup.2                                 Pressure                                                                             137.8                                                                              KPa  ←    59.27                                                                              KPa                                           Temperature                                                                          97-103°                                                                     C.   ←    ←                                             Oil flow                                                                             0.757                                                                              lpm  ←    ←                                             Kinetic energy                                                                       15127                                                                              Joule                                                                              ←    1223 Joule                                         Level  Level                                                                              B    Level                                                                              B    Level                                                                              B                                             Cycies 2000 cycles                                                                             5000 cycles                                                                             200  cycles                                        Speed  3600 rpm  4000 rpm  3600 rpm                                           Inertia                                                                              7.48 kgcmsec.sup.2                                                                      5.00 kgcmsec.sup.2                                                                      3.553                                                                              kgcmsec.sup.2                                 Pressure                                                                             --        --        355.6                                                                              KPa                                           Stop Time                                                                            **0.8                                                                              sec. ***0.95                                                                            sec. --                                                 Temperature                                                                          97-103°                                                                     C.   115-120°                                                                    C.   97-103°                                                                     C.                                            Oil flow                                                                             0.787                                                                              lpm  ←    ←                                             Kinetic energy                                                                       52124                                                                              Joule                                                                              43016                                                                              Joule                                                                              24761                                                                              Joule                                         Power density                                                                        2.89 W/mm.sup.2                                                                         2.01 W/mm.sup.2                                                                         --                                                 __________________________________________________________________________     Note:                                                                         *In level B, adjust apply pressure to maintain 0.8 seconds stop time          within the first 10 cycles.                                                   **In level B, adjust appiy pressure to maintain 0.8 seconds stop time         within the first 10 cycles.                                                   ***In level B1 press start at 140 KPa, adjust the pressure to maintain        0.95 seconds stop time by 90th cycle.                                    

EXAMPLE 18

In the Table 11 below, the high speed durability is shown for theComparatives 3 and 4 and Examples G, H, I and J. The friction materialwas impregnated with a epoxy and modified phenolic resin at about 37%pickup. The shear strength of the Examples G, H and I were comparable toExample J. The compression and compression set showing the strain showsacceptable strength and elasticity which allows for more uniform heatdissipation during use of the friction material since the fluid in thetransmission or brake can rapidly move through the porous structure. Theincreased elasticity also provides more uniform pressure or evenpressure distribution on the friction material such that uneven liningwear or separator plate "hot spots" are eliminated or minimized.

Table 12 below shows high speed durability testing showing the frictionplate condition, separator plate condition and the overall condition ofeach sample. It is to be especially noted that Example I only had lightglazing and pitting and the overall condition was fair with no materialloss.

Table 13 below shows the high speed durability test showing the frictioncoefficient at energy levels A, B and C, the stop-time and the percentof fade. The Comparative 4, Example G and J experienced a break-out andthe test was stopped. The fibrous base material in Examples H and Iperformed well at high speeds. It is important to note that there is no"fall off" of the coefficient of friction as the number of cycleincreases for the fibrous base material in Example I.

                                      TABLE 11                                    __________________________________________________________________________    Material Comp. 3                                                                            Comp. 4                                                                            Ex. G                                                                              Ex. H                                                                              Ex. I                                                                              Ex. J                                       __________________________________________________________________________    Raw paper                                                                               25.86                                                                             26.29                                                                               5.46                                                                               6.00                                                                               7.84                                                                              --                                          pore size (μm)                                                             permeability (cm.sup.2)                                                                 0.516                                                                              0.653                                                                              0.077                                                                              0.115                                                                              0.127                                                                             --                                          32861, 37% p/u                                                                          15.09                                                                             23.90                                                                               4.32                                                                               5.35                                                                               7.04                                                                               9.88                                       pore size (μm)                                                             permeability (cm.sup.2)                                                                 0.225                                                                              0.295                                                                              0.030                                                                              0.054                                                                              0.115                                                                             --                                          Shear strength (psi)                                                                   127.2                                                                              87.9 354.6                                                                              318.8                                                                              339.5                                                                              359.8                                       300 ps comp/set                                                                         0.1222/                                                                            0.1448/                                                                            0.0475/                                                                            0.0528/                                                                            0.0546/                                                                            0.0698/                                    (strain)  0.0232                                                                             0.0309                                                                             0.0002                                                                             0.0030                                                                             0.0015                                                                             0.0106                                     1500 psi comp/set                                                                       0.2999/                                                                            0.2955/                                                                            0.1946/                                                                            0.1721/                                                                            0.2321/                                                                            0.1988/                                    (strain)  0.1049                                                                             0.0821                                                                             0.0510                                                                             0.0414                                                                             0.0482                                                                             0.0362                                     __________________________________________________________________________

                                      TABLE 12                                    __________________________________________________________________________    High Speed Durability Test                                                    (Procedure 5004A)                                                             Friction                                                                      Tests Comp. 3                                                                             Comp. 4                                                                             Ex. G Ex. H                                                                              Ex. I Ex. J                                      __________________________________________________________________________    Total wear                                                                          0.0168                                                                              impossible                                                                          impossible                                                                          0.0269                                                                             0.0081                                                                              impossible                                 (inch)                                                                        Friction plate                                                                      light glazing                                                                       heavy heavy glazing                                                                            glazing                                                                             heavy                                      condition                                                                           & pitting                                                                           material loss                                                                       material loss                                                                       pitting                                                                            light pitting                                                                       materiai loss                                                      breakout                                              Separator                                                                           dark heat                                                                           heat stain                                                                          heat stain                                                                          heat stain                                                                         heat stalight                                                                       heat stains                                plate stain hot spots   hot spots                                                                          hot spots                                        condition                                                                     Overall                                                                             poor  not complete                                                                        not complete                                                                        fair fair  poor                                       condition                                                                     __________________________________________________________________________

                                      TABLE 13                                    __________________________________________________________________________    High Speed Durability Test                                                    (Procedure 5004A)                                                             Friction                                                                      Coefficients                                                                           Comp. 3                                                                             Comp. 4                                                                            Ex. G                                                                              Ex. H                                                                             Ex. I                                                                            Ex. J                                         __________________________________________________________________________    Level A                                                                            μs                                                                             0.092 0.099                                                                              0.099                                                                              0.101                                                                             0.095                                                                            0.103                                         (50  μi                                                                             0.153 0.173                                                                              0.141                                                                              0.152                                                                             0.129                                                                            0.161                                         cycles)                                                                            μd                                                                             0.130 0.132                                                                              0.136                                                                              0.136                                                                             0.128                                                                            0.141                                              μO                                                                             0.141 0.134                                                                              0.149                                                                              0.147                                                                             0.133                                                                            0.145                                              μO/μd                                                                       1.085 1.015                                                                              1.095                                                                              1.081                                                                             1.039                                                                            1.028                                         Level B                                                                            μs                                                                             0.071 787  592 cycles                                                                         0.086                                                                             0.081                                                                            101 cycles                                    (2050                                                                              μi                                                                             0.127 cycles                                                                             break-out                                                                          0.133                                                                             0.136                                                                            break-but                                     cycles)                                                                            μd                                                                             0.127 break-                                                                             stop 0.124                                                                             0.126                                                                            stop                                               μO                                                                             0.122 out       0.128                                                                             0.124                                                 μO/μd                                                                       0.961 stop      1.032                                                                             0.984                                            Level C                                                                            μs                                                                             0.106 --   --   0.102                                                                             0.101                                                                            --                                            (2100                                                                              μ                                                                              0.163 --   --   0.161                                                                             0.160                                                                            --                                            cycles)                                                                            μd                                                                             0.148 --   --   0.146                                                                             0.148                                                                            --                                                 μO                                                                             0.149 --   --   0.141                                                                             0.149                                                                            --                                                 μ)/μd                                                                       1.007 --   --   0.966                                                                             1.007                                                                            --                                            Stop-time                                                                          A   0.916 0.917                                                                              0.917                                                                              0.891                                                                             0.958                                                                            0.855                                         (sec)                                                                              B   0.803 --   --   0.814                                                                             0.792                                                                            --                                                 C   0.805 --   --   0.856                                                                             0.835                                                                            --                                            Fade %                                                                             μd                                                                             -0.8  --   --   -5.3                                                                              -3.8                                                                             --                                            stop time                                                                              +0.1  --   --   -0.2                                                                              +0.6                                                                             --                                            __________________________________________________________________________

EXAMPLE 19

The high energy durability tests are shown in Tables 14, 15 and 16 belowfor the Comparatives 3 and 4 and Examples G, H, I and J impregnated withthe epoxy modified phenolic resin. It is noted that the amount of resinpick-up varies for different examples. In Table 14, the compression andcompression set data show acceptable values for the Examples G, H, I andJ.

Table 15 shows the friction plate condition, the separator platecondition and the overall condition. It is to be noted that Example Ishowed only a slight abrasion, glazing and pitting and that theseparator plate had few hot spots or heat strains.

Table 16 below shows the friction coefficient for levels A, B and C, thestop time and percent rate. As can be seen, the examples of the presentinvention perform consistently better than the comparative materials.Thus, the fibrous base materials of the present invention performed muchbetter at higher speeds than the comparative materials. It is alsoimportant to note that there is no fall off of coefficient of frictionas the number of cycles increases for the fibrous base materials ofExample I. Also, the relatively steady coefficient of friction indicatesthe friction materials are very stable.

                                      TABLE 14                                    __________________________________________________________________________    High Energy Durability Test                                                   (Procedure 5003A)                                                             Material Comp. 3                                                                             Comp. 4                                                                             Ex. G                                                                              Ex. H                                                                              Ex. I                                                                              Ex. J                                     __________________________________________________________________________    Raw paper                                                                               25.86                                                                               26.29                                                                               5.46                                                                               6.00                                                                               7.84                                                                              --                                        pore size (μm)                                                             permeability (cm.sup.2)                                                                 0.516                                                                               0.653                                                                               0.077                                                                              0.115                                                                              0.127                                                                             --                                        resin 37% p/u                                                                           20.03                                                                               22.44                                                                               4.32                                                                               5.35                                                                               7.04                                                                               9.33                                     pore size (μm)                                                                      (53.2% pu)                                                                          (54.9% pu)                                                                          (37% pu)                                                                           (35% pu)                                                                           (37% pu)                                       permeability (cm.sup.2)                                                                --    --     0.030                                                                              0.054                                                                              0.115                                                                             --                                        Shear strength (psi)                                                                   224.2 177.9 354.6                                                                              318.8                                                                              339.5                                                                              359.8                                     300 psi comp/set                                                                        0.1016/                                                                             0.1563/                                                                             0.0475/                                                                            0.0528/                                                                            0.05461                                                                            0.0698/                                  (strain)  0.0122                                                                              0.0323                                                                              0.0002                                                                             0.0030                                                                             0.0015                                                                             0.0106                                   1500 psi comp/set                                                                       0.28861                                                                             0.3746/                                                                             0.1946/                                                                            0.1721/                                                                            0.2321/                                                                            0.1988/                                  (strain)  0.0627                                                                              0.0934                                                                              0.0510                                                                             0.0414                                                                             0.0482                                                                             0.0362                                   __________________________________________________________________________

                                      TABLE 15                                    __________________________________________________________________________    High Speed Durability Test                                                    (Procedure 5003A)                                                             Friction                                                                      Tests Comp. 3                                                                             Comp. 4                                                                             Ex. G Ex. H Ex. I Ex. J                                     __________________________________________________________________________    Total wear                                                                          0.0205                                                                              0.0245                                                                              impossible                                                                          0.0242                                                                              0.0256                                                                              0.0192                                    (inch)                                                                        Friction plate                                                                      light glazing                                                                       glazing                                                                             heavy heavy glaze                                                                         glazing                                                                             glazing                                   condition                                                                           & pitting                                                                           light pitting                                                                       material loss                                                                       & abrasions                                                                         abrasion                                                                            abrasion                                                          breakout                                                                            slight pitting                                  Separator                                                                           heat stain                                                                          heat stain                                                                          heat stain                                                                          mid wear                                                                            mid wear                                                                            heat stained                              plate few hot spots                                                                       few hot spots                                                                       hot spots                                                                           mark & heat                                                                         mark few hot                                                                        hot spots                                 condition               stains heavy                                                                        spots heat                                                              abrasion                                                                            stains                                          Overall                                                                             fair 1                                                                              fair 2                                                                              not complete                                                                        poor  fair 2                                                                              fair                                      condition                                                                     __________________________________________________________________________

                                      TABLE 16                                    __________________________________________________________________________    High Energy Durability Test                                                   (Procedure 5003A)                                                             Friction                                                                      Coefficients                                                                           Comp. 3                                                                            Comp. 4                                                                            Ex. G                                                                              Ex. H                                                                              Ex. I                                                                             Ex. J                                        __________________________________________________________________________    Level A                                                                            μs                                                                             0.102                                                                              0.03 0.111                                                                              0.101                                                                              0.104                                                                             0.121                                        (50  μi                                                                             (0.141)                                                                            (0.240)                                                                            0.145                                                                              0.148                                                                              (0.137)                                                                           0.146                                        cycles)                                                                            μd                                                                             0.131                                                                              0.124                                                                              0.141                                                                              0.131                                                                              0.130                                                                             0.136                                             μO                                                                             0.142                                                                              0.136                                                                              0.145                                                                              0.143                                                                              0.140                                                                             0.149                                             μO/μd                                                                       1.084                                                                              1.097                                                                              1.028                                                                              1.091                                                                              1.077                                                                             1.096                                        Level B                                                                            μs                                                                             0.101                                                                              0.101                                                                              124 cycles                                                                         0.093                                                                              0.103                                                                             0.097                                        (2050                                                                              μi                                                                             0.137                                                                              0.129                                                                              break-out                                                                          0.127                                                                              0.128                                                                             0.141                                        cycles)                                                                            μd                                                                             0.137                                                                              0.129                                                                              stop 0.128                                                                              0.130                                                                             0.132                                             μO                                                                             0.142                                                                              0.123     0.131                                                                              0.128                                                                             0.146                                             μO/μd                                                                       1.036                                                                              0.953     1.023                                                                              0.985                                                                             0.106                                        Level C                                                                            μs                                                                             0.115                                                                              0.114                                                                              --   0.100                                                                              0.108                                                                             0.103                                        (2100                                                                              μi                                                                             0.174                                                                              0.160                                                                              --   0.152                                                                              0.154                                                                             0.173                                        cycles)                                                                            μd                                                                             0.152                                                                              0.151                                                                              --   0.145                                                                              0.150                                                                             0.149                                             μO                                                                             6.152                                                                              0.155                                                                              --   0.142                                                                              0.150                                                                             0.144                                             μO/μd                                                                       1.000                                                                              1.026                                                                              --   0.979                                                                              1.000                                                                             0.966                                        Stop-time                                                                          A   0.867                                                                              0.913                                                                              0.863                                                                              0.878                                                                              0.888                                                                             0.840                                        (sec)                                                                              B   0.756                                                                              0.778                                                                              --   0.816                                                                              0.807                                                                             0.773                                             C   0.800                                                                              0.812                                                                              --   0.841                                                                              0.843                                                                             0.830                                        Fade %                                                                             μd                                                                             +3.0 -0.8 --   -4.5 -3.0                                                                              -2.2                                         stop time                                                                              -5.7 -2.5 --   +1.7 +1.4                                                                              -4.0                                         __________________________________________________________________________

EXAMPLE 20

High energy durability tests were also conducted for Examples I and Jusing different resins and different percentages of resins. It is to benoted that the shear strengths vary slightly with the type of resin, butthat the shear strengths are consistently acceptable. The compressionand compression set data indicate a better performance by Example I overthe Example J. The coefficient of friction levels, for example, I isimpregnated with a phenolic resin which shows better results than theother tested examples. Again, there is no "fall off" shown for Example Iin Table 17 below.

                                      TABLE 17                                    __________________________________________________________________________    High Energy Durability Test                                                   (Procedure 5030A)                                                                       Ex. I  Ex. J  Ex. I  Ex. J                                          __________________________________________________________________________    Resin     295 D-2                                                                              295 b-2                                                                              32861  32861                                          Pick-up   35%    36%    39.7%  40.7%                                          Shear psi 340    356    254    301                                            Comp/comp-set                                                                           0.050/0.006                                                                          0.053/0.008                                                                          0.066/0.015                                                                          0.059/0.008                                    300 psi/1500 psi                                                                        0.147/0.016                                                                          0.192/0.036                                                                          0.217/0.047                                                                          0.220/0.049                                    Total wear (in.)                                                                        0.0106 0.0142 --     --                                             Level A                                                                             μs                                                                             0.094  0.097  0.095  0.109/0.092                                    50 cycles                                                                           μi                                                                             0.132  0.130  0.131  0.157/0.146                                          μd                                                                             0.132  0.132  0.121  0.129/0.120                                          μO                                                                             0.140  0.136  0.133  0.144/0.136                                    Level B                                                                             μs                                                                             0.077  Stopped test at                                                                      Failed at 110                                                                        Failed at                                      5050 cycles                                                                         μi                                                                             0.102  3378 cycles                                                                          cycles 100 & 125 cycles                                     μd                                                                             0.101  Stop-time                                                          μO                                                                             0.113  1.244 sec.                                                   Level C                                                                             μs                                                                             0.103  --     --     --                                             5100 cycle                                                                          μi                                                                             0.147  --     --     --                                                   μd                                                                             0.120  --     --     --                                                   μO                                                                             0.139  --     --     --                                             Stop-time                                                                           A   0.825  0.861  0.916  08.54/0.927                                    (sec.)                                                                              B   1.109  --     --     --                                                   C   0.923  --     --     --                                             Stop-time Fade                                                                          4000 cycles                                                                          2100 cycles                                                                          --     --                                             15% cycles                                                                    __________________________________________________________________________

In the Examples 21-23 below, each of the following fibrous basematerials is a formulation which comprises, in percent, by weight, about23% synthetic graphite, about 27% diatomaceous earth, about 5% aramidfiber pulp and varying types of fibers:

Example K about 45% aramid fibers--(CSF between about 580-640);

Example L about 45% aramid fibers--(CSF between about 450-500);

Example M about 45% aramid fibers--(CSF between about 580-640);

Example N about 45% aramid fibers--(CSF between about 450-500); and

Example O about 45% aramid fibers--(CSF between about 580-640).

EXAMPLE 21

Examples K and L shown in Table 18 below were saturated with about 48%and 46%, pick-up, respectively, with a resin blend of 50% silicone andabout 50% phenolic resin. The shear strength and the compression andcompression set data show that Example K comprising the less fibrillatedaramid fibers is comparable to Example L.

FIG. 23 shows the pore size of Example L, while FIG. 24 shows the poresize for Example K.

                  TABLE 18                                                        ______________________________________                                                   Ex. K       Ex. L                                                  ______________________________________                                        Resin        silicone/phenolic                                                                           silicone/phenolic                                               mixed resin   mixed resin                                                     48% PU        46% PU                                             Raw paper    6.00          6.28                                               pore size (μm)                                                             Graphite     1.3/2.8       2.4/5.1                                            concentration                                                                 Felt/wire (%)                                                                 Saturated paper                                                                            5.99          5.20                                               pore size (μm)                                                             shear strength                                                                             313           422                                                (psi)                                                                         Comp/Comp-set                                                                              0.074/0.016   0.059/0.008                                        (strain)     0.210/0.042   0.172/0.027                                        300/1500 psi                                                                  ______________________________________                                    

EXAMPLE 22

The high speed durability test under Procedure 5004C for Examples K, L,M and N are shown in Tables 19 and 20 below. The friction platecondition showed only medium to light glaze and the separator platecondition showed medium heat stains for the fibrous base materialcontaining less fibrillated aramid fibers (CSF about 580-640). Thecoefficient of friction for levels A, B and C indicate that the fibrousbase materials perform consistently. The stop time and percent fade wasabout 3 to 4 times better for Exhibit K than for Exhibit L. The stoptime for Exhibit M was at least about 4 times better than for Exhibit N,and the percent fade was more than two times better for Exhibit M thanfor Exhibit N.

                  TABLE 19                                                        ______________________________________                                        High Speed Durability Test                                                    (Procedure 5004C)                                                             ______________________________________                                        Resin        48% PU         46% PU                                            Total wear (in.)                                                                           0.0056         0.0068                                            Friction plate                                                                             Medium glaze   Light to Medium                                   condition                   glaze                                             Separator plate                                                                            Medium heat stains                                                                           Medium to heavy                                   condition    heat stains                                                      Level A   μS  0.095           0.104                                        50 cycles μi  0.135          (0.146)                                                 μd  0.119           6.129                                                  μO  0.123           0.132                                        Level B   μS  0.095           0.094                                        5050 cycles                                                                             μi  0.116           0.110                                                  μd  0.115           0.112                                                  μO  0.122           0.121                                        Level C   μS  0.115           0.113                                        5100 cycles                                                                             μi  0.137           0.134                                                  μd  0.122           0.116                                                  μO  0.129           0.123                                        Stop-time A      0.946           0.885                                        (sec.)    B      0.827           0.914                                                  C      0.932           0.957                                        Stop-time fade                                                                             3.5%           12.8%                                             μd fade (%)                                                                             5.7%           14.5%                                             ______________________________________                                    

                  TABLE 20                                                        ______________________________________                                        High Speed Durability Test                                                    (Procedure 5004C)                                                                        Ex. M        Ex. N                                                 ______________________________________                                        Resin        41% PU         42% PU                                            Total wear (in.)                                                                           0.0077         0.9069                                            Friction plate                                                                             Medium glaze   Medium glazing &                                  condition                   abrasion                                          Separator plate                                                                            Medium heat stains                                                                           Medium heat                                       condition    hot spots, light                                                                             stains hot spots                                               abrasion                                                         Level A   μS  0.095           0.095                                        50 cycles μi  0.148           0.153                                                  μd  0.118           0.119                                                  μO  0.121           0.123                                        Level B   μS  0.086           0.084                                        5050 cycles                                                                             μi  0.112           0.113                                                  μd  0.110           0.112                                                  μO  0.119           0.118                                        Level C   μS  0.109           0.105                                        5100 cycles                                                                             μi  0.145           0.143                                                  μd  0.119           0.122                                                  μO  0.126           0.126                                        Stop-time A      0.965           0.922                                        (sec.)    B      0.829           0.881                                                  C      0.938           0.924                                        Stop-time fade                                                                             1.6%            7.6%                                             pd fade (%)  5.2%           11.8%                                             ______________________________________                                    

EXAMPLE 23

The break-in characteristics are shown in Table 21 below for Examples K,L and 0. The break-in characteristics indicate good behavioralcharacteristics and low wear.

                  TABLE 21                                                        ______________________________________                                        Break-In Characteristic Test                                                  (Procedure 5004D)                                                                             48% PU                                                                              46% PU                                                  Type of Fiber                                                                              Ex. K        Ex. O  Ex. L                                        ______________________________________                                        1 cycles  μS  0.092        0.104                                                                              0.117                                                μi  0.106        0.117                                                                              0.127                                                μd  0.092        0.108                                                                              0.114                                                μO  0.096        0.103                                                                              0.111                                      50 cycles μS  0.102        0.098                                                                              0.099                                                μi  0.143        0.142                                                                              0.161                                                μd  0.116        0.115                                                                              0.133                                                μO  0.121        0.118                                                                              0.131                                      200 cycles                                                                              μS  0.097        0.097                                                                              0.105                                                μi  0.146        0.145                                                                              0.160                                                μd  0.123        0.123                                                                              0.142                                                μO  0.128        0.122                                                                              0.139                                      Stop-time  1     1.104        1.093                                                                              1.015                                      (sec.)     50    0.962        0.988                                                                              0.868                                                200    0.919        0.946                                                                              0.828                                      Total Wear       0.0011       0.001                                                                              0.0012                                     (in.)                                                                         ______________________________________                                    

INDUSTRIAL APPLICABILITY

The present invention is useful as a high energy friction material foruse with clutch plates, transmission bands, brake shoes, synchronizerrings, friction disks or system plates.

The above descriptions of the preferred and alternative embodiments ofthe present invention are intended to be illustrative and are notintended to be limiting upon the scope and content of the followingclaims.

We claim:
 1. A fibrous base material for use in a non-asbestos frictionmaterial comprising a plurality of less fibrillated aramid fibers havinga freeness of at least about 530 on the Canadian Standard Freeness (CSF)index; synthetic graphite; and, at least one filler material.
 2. Thefibrous base material of claim 1, wherein the less fibrillated aramidfiber and synthetic graphite are present in amounts sufficient toprovide high heat resistance and substantially uniform coefficient offriction to the friction material.
 3. The fibrous base material of claim1, wherein the less fibrillated aramid fibers have a freeness about580-640 on the Canadian Standard Freeness index.
 4. The fibrous basematerial of claim 1, wherein the synthetic graphite is made bygraphitization at temperatures of about 2800°-3,000° C. and has a sizeranging from about 20 to about 50 microns in diameter.
 5. The fibrousbase material of claim 1, wherein the less fibrillated aramid fibershave average fiber lengths in the range of 0.5 mm to 6 mm.
 6. Thefibrous base material of claim 1, wherein the filler comprisesdiatomaceous earth.
 7. The fibrous base material of claim 1, wherein thefibrous base material defines pores ranging in mean average size fromabout 2.0 to about 15 microns in diameter.
 8. The friction member ofclaim 1, wherein the friction material has readily available air voidsof at least about 50%.
 9. The fibrous base material of claim 1comprising about 10 to about 50%, by weight, less fibrillated aramidfiber; about 10 to about 35, by weight, synthetic graphite; and about 20to about 45%, by weight, filler material.
 10. The fibrous base materialof claim 1 comprising in percent, by weight, about 20 to about 30% lessfibrilated aramid fibers, about 10 to about 35% synthetic graphite,about 20 to about 30% filler, and about 0 to about 40% cotton fibers.11. The friction material of claim 10, wherein the fibrous base materialcomprises about 20% to about 40% cotton fibers.
 12. A non-asbestosfriction material comprising the fibrous base material of claim 1impregnated with a phenolic resin or a modified phenolic resin.
 13. Thefriction material of claim 12, wherein the friction material comprisesapproximately 40 to about 60% resin, by weight.
 14. A non-asbestosfriction material comprising the fibrous base material of claim 1impregnated with a mixture of a phenolic resin and a silicone resinwherein the amount of silicone resin in the mixture ranges fromapproximately 5 to approximately 80%, by weight, based on the weight ofthe mixture, the friction material exhibiting high heat resistance andsubstantially uniform coefficient of friction.
 15. The friction materialof claim 14, wherein the phenolic resin is present in a solvent materialand the silicone resin is present in a solvent material which iscompatible with the solvent material of the phenolic resin.
 16. Thefriction material of claim 14, wherein the amount of silicone resinpresent in the silicone-phenolic resin mixture ranges from about 20 toabout 25%, by weight, based on the weight of the mixture.
 17. Thefriction material of claim 14, wherein the amount of silicone resinpresent in the silicone phenolic resin mixture ranges from about 15 toabout 25%, by weight, based on the weight of the mixture.
 18. Thefriction material of claim 12, wherein the modified phenolic resincomprises an epoxy phenolic resin.
 19. The friction material of claim18, wherein the amount of epoxy resin present in the epoxy phenolicresin ranges from about 5 to about 25%, by weight, based on the weightof the epoxy phenolic resin.
 20. The friction material of claim 18,wherein the amount of epoxy resin present in the epoxy phenolic resinranges from about 10 to about 15%, by weight, based on the weight of theepoxy phenolic resin.
 21. A process for producing a non-asbestosfriction material comprising mixing less fibrillated aramid fibershaving a freeness of at least about 530 on the Canadian StandardFreeness (CSF) index with synthetic graphite and at least one filler toform a fibrous base material, impregnating the fibrous base materialwith a phenolic resin or modified phenolic resin, and thereafter curingthe impregnated fibrous base material at a predetermined temperature fora predetermined period of time.
 22. A process for producing anon-asbestos friction material comprising mixing a phenolic resin with asilicone resin, impregnating the fibrous base material of claim 1 withthe silicone-phenolic resin mixture, and thereafter heating theimpregnated fibrous base material to cure the phenolic resin and thesilicone resin.